1. Field of the Invention
The present invention relates to a display device, and particularly, to a tiled display device capable of achieving uniform brightness over an entire area of a large display screen.
2. Discussion of the Related Art
With the increase in popularity of visual information transmitting devices, electronic display devices have been actively developed and researched. A liquid crystal display (LCD) device, one of the electronic display devices, is in great demand because it is slim, lightweight and efficient in power-consumption. Also, with the improvement in living standards, an LCD device with a large size and high image quality has lately attracted considerable attention.
There are limitations to how large the LCD screen can be because of the characteristics of the LCD device. For this reason, a projection TV having an optical system with a small liquid crystal panel and implementing a large image on a screen by magnifying and projecting an image on the screen has been proposed. Recently, a tiled LCD device in which a plurality of LCD devices are tiled together with their side surfaces contacting each other to form a large size display device is being put to practical use. As disclosed in U.S. Pat. Nos. 4,980,755, 5,067,021, 5,068,740 and 5,079,636, a tiled LCD device is fabricated by tiling at least two liquid crystal panels side by side. The key to a technology for fabricating such a tiled LCD device is to prevent boundary lines between a plurality of LCD devices from being displayed on a screen.
In general, the tiled display device is formed by fixing a plurality of display devices to a support frame. Here, each display device serves as one unit when a backlight assembly, a display panel, a polarization member, and the like are attached thereto. The support frame includes an outer wall frame, a partition wall frame interposed between the plurality of display devices and a bottom plate receiving the partition wall frame and the display devices. Here, each display device is received in a space formed by the partition wall frame and the outer wall frame and is thus tiled.
However, in a large screen formed through the aforementioned tiling technology, since an image is not formed at a partition wall frame area, a boundary display phenomena, namely, a seam phenomenon (artificial boundary), occurs in that a boundary line between the display devices is displayed on the screen along the partition wall frame. Thus, an entirely-unified image cannot be displayed. Accordingly, in order to prevent a seam line from being displayed at a seam area between display devices, namely, at a support frame area, a method of preventing seam phenomena has been proposed by guiding light emitted from the display panels of the display devices and thus extending a path of the light to an upper portion of the support frame. In this method, a light-guide lens is employed to guide the light.
The light-guide lens is made of glass or transparent plastic having good light transmittance. Also, the light-guide lens is shaped as a triangular prism or a semi-circular cylinder, a portion of which has a predetermined curvature. Such a light-guide lens is installed in close proximity to an upper portion of the display device and diffuses light having passed through the display device up to a screen of a tiled display device having a large screen.
However, in the tiled display device, a path of light having passed through a curved (rounded) portion of the light-guide lens is diffused because of distortion of the curved portion, thereby implementing an image over a seam area. Here, problems occur in that the brightness above the seam area is lower than the average brightness of a panel because of the diffusion of light. Therefore, a device for solving the problems of non-uniform brightness and achieving entirely uniform brightness distribution is required.